Ko Tarutao island is the largest island of the Tarutao National Park in Satun Province of southern Thailand.

The island is 26 km (16 mi) long and 11 km (7 mi) wide. It is one of the most unspoiled islands in Andaman Sea and in all of Thailand. Ko Tarutao is located about 10 km (6 mi) north of Langkawi Island in Malaysia. The Malay word tertua or tarutao means old and primitive.